Android：获取应用信息，打开、卸载应用

在项目里有一个需求，点击App介绍里面的官方微信公众号，就可以直接打开微信搜索、关注。这个功能实现起来并不复杂，获取包名，用intent跳转即可。那么如何获取某一个应用的包名呢？可以反编译apk，在文件里查看，这个方法比较麻烦。我们也可以直接通过Android系统为我们提供的类PackageManager来获得PackageInfo，这个类里面包含相关应用程序的很多信息。示例用到了SwipeMenuListView，菜单里提供打开App与卸载App两个功能。主要示例代码如下：

package com.li.applistdemo;

import android.content.ComponentName;
import android.content.Intent;
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageInfo;
import android.content.pm.ResolveInfo;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.TypedValue;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import com.baoyz.swipemenulistview.BaseSwipListAdapter;
import com.baoyz.swipemenulistview.SwipeMenu;
import com.baoyz.swipemenulistview.SwipeMenuCreator;
import com.baoyz.swipemenulistview.SwipeMenuItem;
import com.baoyz.swipemenulistview.SwipeMenuListView;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    public final int GET_ALL_APP = 0; // 所有应用程序
    public final int GET_SYSTEM_APP = 1; // 系统程序
    public final int GET_THIRD_APP = 2; // 第三方应用程序
    public final int GET_SDCARD_APP = 3; // 安装在SDCard的应用程序

    private List<PackageInfo> mAppList;
    private AppListAdapter mAdapter;
    private SwipeMenuListView mListView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mAppList = getPackageInfos(GET_THIRD_APP);

        mListView = (SwipeMenuListView) findViewById(R.id.swipeListView);
        mAdapter = new AppListAdapter();
        mListView.setAdapter(mAdapter);

        SwipeMenuCreator creator = new SwipeMenuCreator() {
            @Override
            public void create(SwipeMenu menu) {
                SwipeMenuItem openItem = new SwipeMenuItem(
                        getApplicationContext());
                openItem.setBackground(new ColorDrawable(Color.rgb(0xC9, 0xC9,0xCE)));
                openItem.setWidth(dp2px(100));
                openItem.setTitle("Open");
                openItem.setTitleSize(18);
                openItem.setTitleColor(Color.WHITE);
                menu.addMenuItem(openItem);

                SwipeMenuItem deleteItem = new SwipeMenuItem(
                        getApplicationContext());
                deleteItem.setBackground(new ColorDrawable(Color.rgb(0xF9, 0x3F, 0x25)));
                deleteItem.setWidth(dp2px(100));
                deleteItem.setIcon(R.mipmap.ic_delete);
                menu.addMenuItem(deleteItem);
            }
        };

        mListView.setMenuCreator(creator);

        mListView.setOnMenuItemClickListener(new SwipeMenuListView.OnMenuItemClickListener() {
            @Override
            public boolean onMenuItemClick(int position, SwipeMenu menu, int index) {
                PackageInfo item = mAppList.get(position);
                switch (index) {
                    case 0:
                        open(item);
                        break;
                    case 1:
                        uninstall(item);
                        mAppList.remove(position);
                        mAdapter.notifyDataSetChanged();
                        break;
                }
                return false;
            }
        });
    }

    private List<PackageInfo> getPackageInfos(int type){
        // 0 表示不接受任何参数。其他参数都带有限制
        // 版本号、APP权限只能通过PackageInfo获取，所以这里不使用getInstalledApplications()方法
        List<PackageInfo> packageInfos = getPackageManager().getInstalledPackages(0);
        if (packageInfos == null){
            return null;
        }

        List<PackageInfo> result = new ArrayList<>();
        switch (type) {
            case GET_ALL_APP:
                result = packageInfos;
                break;
            case GET_SYSTEM_APP: // 系统自带APP
                for (PackageInfo info : packageInfos) {
                    // FLAG_SYSTEM = 1<<0，if set, this application is installed in
                    // the device's system image.
                    // 下面&运算有两种结果：
                    // 1，则flags的末位为1，即系统APP
                    // 0，则flags的末位为0，即非系统APP
                    if ((info.applicationInfo.flags & ApplicationInfo.FLAG_SYSTEM) == 1) {
                        result.add(info);
                    }
                }
                break;
            case GET_THIRD_APP: // 第三方APP
                for (PackageInfo info : packageInfos) {
                    // FLAG_SYSTEM = 1<<0，同上
                    if ((info.applicationInfo.flags & ApplicationInfo.FLAG_SYSTEM) == 0) {
                        result.add(info);
                    }
                    // 本来是系统程序，被用户手动更新后，该系统程序也成为第三方应用程序了
                    // FLAG_UPDATED_SYSTEM_APP = 1<<7， this is set if this
                    // application has been
                    // install as an update to a built-in system application.
                    else if ((info.applicationInfo.flags & ApplicationInfo.FLAG_UPDATED_SYSTEM_APP) == 1) {
                        result.add(info);
                    }
                }
                break;
            case GET_SDCARD_APP: // 安装在SDCard的应用程序
                for (PackageInfo info : packageInfos) {
                    // FLAG_EXTERNAL_STORAGE = 1<<18，Set to true if the application
                    // is
                    // currently installed on external/removable/unprotected storage
                    if ((info.applicationInfo.flags & ApplicationInfo.FLAG_EXTERNAL_STORAGE) == 1) {
                        result.add(info);
                    }
                }
                break;
        }
        return result;
    }

    private void uninstall(PackageInfo item) {
        try {
            Intent intent = new Intent(Intent.ACTION_DELETE);
            intent.setData(Uri.fromParts("package", item.packageName, null));
            startActivity(intent);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void open(PackageInfo item) {
        Intent resolveIntent = new Intent(Intent.ACTION_MAIN, null);
        resolveIntent.addCategory(Intent.CATEGORY_LAUNCHER);
        resolveIntent.setPackage(item.packageName);
        List<ResolveInfo> resolveInfoList = getPackageManager()
                .queryIntentActivities(resolveIntent, 0);
        if (resolveInfoList != null && resolveInfoList.size() > 0) {
            ResolveInfo resolveInfo = resolveInfoList.get(0);
            String activityPackageName = resolveInfo.activityInfo.packageName;
            String className = resolveInfo.activityInfo.name;

            Intent intent = new Intent(Intent.ACTION_MAIN);
            intent.addCategory(Intent.CATEGORY_LAUNCHER);
            ComponentName componentName = new ComponentName(
                    activityPackageName, className);

            intent.setComponent(componentName);
            startActivity(intent);
        }
    }

    class AppListAdapter extends BaseSwipListAdapter {

        @Override
        public int getCount() {
            return mAppList.size();
        }

        @Override
        public PackageInfo getItem(int position) {
            return mAppList.get(position);
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            if (convertView == null) {
                convertView = View.inflate(getApplicationContext(),
                        R.layout.item_list_app, null);
                new ViewHolder(convertView);
            }
            ViewHolder holder = (ViewHolder) convertView.getTag();
            PackageInfo item = getItem(position);

            holder.iv_icon.setImageDrawable(item.applicationInfo.loadIcon(getPackageManager()));
            holder.tv_name.setText(item.applicationInfo.loadLabel(getPackageManager()) + "\n" + item.packageName);

            return convertView;
        }

        class ViewHolder {
            ImageView iv_icon;
            TextView tv_name;

            public ViewHolder(View view) {
                iv_icon = (ImageView) view.findViewById(R.id.iv_icon);
                tv_name = (TextView) view.findViewById(R.id.tv_name);
                view.setTag(this);
            }
        }

        @Override
        public boolean getSwipEnableByPosition(int position) {
            return true;
        }
    }

    private int dp2px(int dp) {
        return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp,
                getResources().getDisplayMetrics());
    }
}

获取App列表信息比较耗时，可能会引起ANR，所以这些操作应该放在子线程里面。

获取到结果以后，我们要通过Adapter来更新UI，但是Android不允许在非UI线程里面更新UI，可以用Handler去post一个Runnable对象来解决这个问题。为什么Handler可以呢？感兴趣的可以看看 http://blog.csdn.net/ly502541243/article/details/52062179/ ，里面分析得很详细。
简单来说，通过Handler.post(Runnable r)传入的Runnable，在回调的时候会调用run方法，而直接调用线程的run方法相当于是在一个普通的类调用方法，还是在当前线程执行，并不会开启新的线程。在post中传了个Runnable，还是在主线程中，因此可以更新UI。